It's not that either is impossible or even improbable, it's just that it forces us to revisit everything again to try and work out the routes if these (and other similarly early dates that have been proposed in the last couple years) hold up under review.
Anyway, the current understanding of the paleoclimate is that entire region between approximately Valdez and Vancouver Island was entirely covered by glaciers out to the edge of continental shelf until ~18kya. Lesnek et al has some good diagrams [1]. Living exclusively off deep-sea marine resources in an iceberge minefield without fire for over a thousand miles in one of the coldest, most dangerous oceans in the world without landing suggests an unprecedented level of both nautical technology and experience. Where did that come from? We have no good answers right now.
So anything you wanted to bring with you on a land route had to be carried by humans, dogs, or pulled on sleds by humans or dogs.
On a water route you could tow another boat or raft behind full of your stuff. (Rope was invented long before any migration to the Americas).
There was a land bridge due to lower sea levels during the last glaciation. HOW people from Asia populated the Americas is not really the question.
